Unitrack Remote Turnouts and Relays

[Cory Rothlisberger]

Okay, I'm done Googling, I need some help from the experts because I'm having a complete brain fart... 

Working on my control panel and I have these latching relays to control bi-color LEDs to show the lined route on my control panel. How the hell do I wire them so that the relay is triggered when activating the turnout using a DPDT momentary toggle? Connecting the trigger pole on the relay to the center pole on the DPDT does not seem to work.


https://www.amazon.com/HiLetgo-Single-Bistable-Self-Locking-Module/dp/B01HHM5M4M

[Point353]

Could you post a diagram of the connections you've made to the relay module?

[Cory Rothlisberger]

Here's where I'm at right now. Wonder if I'm just barking up the wrong tree trying to use this relay module...

[peteski]

Is there any documentation of what is used as a trigger and how exactly the module is supposed to work??

Is your goal to have the trigger pulse alternate between green and red aspect? I just don't understand what is being done.  What type of turnout switch machine is being used?

Also remember that you will need a current limiting resistor in the LED circuit running from 12V DC. Since only one LED will be on at any time one resistor in the common cathode leg will be sufficient.

EDIT:  I looked over the confusing info on amazon and it looks like this operates like a push-on/push-off switch.  The trigger does not use external voltage. You can connect a momentary switch between the trigger pins, then every time you push it (basically momentarily connect the 2 trigger connector pins), the relay will change state.  I suppose the test button is basically wired in parallel with the trigger connector.

Not sure how you would want to sync this to indicate a turnout position. I don't even know  what brand/type  of switch machine you're using.

[Cory Rothlisberger]

Not sure how you would want to sync this to indicate a turnout position. I don't even know  what brand/type  of switch machine you're using.

N-scale Unitrack remote turnouts. Guess my thought was that there must be some way to connect the trigger to the momentary DPDT toggle which controls the turnout, to trigger the relay to illuminate the LED to show the route.


Noted on the resistors on the LEDs. Already have all that planned out...

[Point353]

N-scale Unitrack remote turnouts. Guess my thought was that there must be some way to connect the trigger to the momentary DPDT toggle which controls the turnout, to trigger the relay to illuminate the LED to show the route.

If you want to use that relay module, the easiest way to interface to it might be by using a 3PDT switch, with the third pole of the switch connected to the external trigger switch input on the relay module.

Alternatively, you might want to investigate using the "GRS" control scheme, which was covered in this thread:
https://www.therailwire.net/forum/index.php?topic=57564.msg792716#msg792716
https://www.therailwire.net/forum/index.php?topic=57564.0

[peteski]

Problem with trying to add a position indicator to Kato Unitrak turnouts is the design of their switch machine (where the polarity of the momentary signal is what throws the switch). Also adding to the complexity is the common-cathode bi-color LED (instead of 2 discrete LEDs.  If you do a Google search for examples of this you will find all sorts of designs. Some even use Hall effect sensors to sense the position of the switch machine's magnetic plunger.  The other complication is that you want to use center-off  DPDT switch.

If you were to use a pair of discrete LEDs and a standard 2-position DPDT switch along with a pushbutton switch, that would make the circuit quite simple (again examples are out on the Interwebs).

[Cory Rothlisberger]

So much for this being simple. Out of frustration last night, I just drilled a hole in the panel to go the DPDT & push button combo route. I'm intrigued to try the 3PDT route, but finding a center off/momentary version of these in miniature form is proving difficult. Going to keep my eyes open.

Thanks for all of your input on this...

[mmagliaro]

The trigger to that module is just a switch across the two pins of that white jack on the board.  Each time it is triggered, it changes state.  If you read carefully, there is an obtuse mention in the Amazon ad about "also can be connected with the trigger switch, and low level trigger.".  That to me means that one of the two pins on that white connector just need to be pulled to ground (temporarily) and it will toggle the state of the relay.  Which means the the other white pin is probably just a GND.

There are a lot of problems, and my short answer is "don't use that module".  If you look up the number on that relay and get the data sheet, you'll find that it is not a latching relay.  So the little module is providing a flip-flop function to latch / unlatch the relay when the button is pushed.  But the state-change is strictly controlled by the one-shot state change that occurs when you temporarily short the two pins of the white connector.  So when power is turned off, there will be no way to make sure that when power comes back on, that relay will be in the correct state.  Most likely, it will come up with the relay de-energized, so all the turnout LEDs will show "red" (or all "green") regardless of their actual state.

I would forget the module, and do this with a true latching DPDT dual-coil relay.  The relay contacts would still be used to light up your red/green LEDs (or anything else you want to use), and it would remember its state after you power off and power on, because the relay itself mechanically stays latched in its position.  Since you are already using a momentary dpdt toggle to control the turnout, wired "crossed over" so it outputs one polarity or the other to the switch machine, we can use that to also control the dual-coil relay.

Here's a diagram.  Everything on the right is how you already have it.  The change is just replacing that module with a latching relay.
DPDT dual-coil latching relays are available in handy, small, DIP pin configurations, so you could mount a lot of them on a small piece of
project PC board under a control panel, and run the LED wires from the relays out to all the LEDs in your panel.  Or, if you are setting this up more like having isolated turnout control indicators in a fascia, you can just mount the one relay near the LEDs and run the power and LED wires right to it.

The LEDs shown in my diagram can be two discrete LEDs, or a bicolor common-anode or common-cathode LED.  The diagram as-is assumes common-cathode.  But you just have to flip the LEDs around, and swap the +12 and GND connections to the LED, in order to accomodate a common-anode bi-color LED. 




And here's an example of a relay that will work.  These are about $2 a piece at Mouser:

https://www.mouser.com/ProductDetail/Panasonic-Industrial-Devices/TQ2-L2-12V?qs=UO%2Fx91QLkSADnfa%252Bj3axbw%3D%3D

[freescopesdad]

Working on my control panel and I have these latching relays to control bi-color LEDs to show the lined route on my control panel. How the hell do I wire them so that the relay is triggered when activating the turnout using a DPDT momentary toggle? Connecting the trigger pole on the relay to the center pole on the DPDT does not seem to work.

Cory, I have been trying to do this exact same thing for a week or so now. I have a Kato n scale layout with about 40 turnouts, and I want to build a control panel depicting my track plan with DPDT momentary (center off) toggles and leds showing state of each turnout. I'm currently using DCC Concepts stationary decoders, but of course I can never tell the state of each turnout without physically looking. It is an around the wall 17x17 foot btw. If you ever get this to work please send me a pm or post. I certainly appreciate mmagliaro posting that schematic, but one look and I'm totally lost. I can handle the DPDP momentary toggle wiring but that is about it.
Ron

[Point353]

I'm intrigued to try the 3PDT route, but finding a center off/momentary version of these in miniature form is proving difficult. Going to keep my eyes open.

https://www.digikey.com/en/products/detail/e-switch/1003P4T6B11M1QEH/4027465

[mmagliaro]

A 3 pole switch would be very simple.  But I still don't see how it solves the problem.  That relay module works by shorting the two pins of the white connector together, and all that does is toggle the state.  Each time you push the momentary 3-pole toggle left or right, that extra pole could be used to trigger the relay.
But what about the state?  Those modules likely power up with the relay de-energized.  So let's say that lights the "red" or "diverging route" led. 
So on layout power-up, all the turnout LEDs will be red, which will not be correct.   And if you happen to push a toggle to the left when the turnout is already aligned that way, the relay will still toggle and change the LED to green even though the turnout does not move.
I am envisioning a nice little etched PC board, with the latching relay on it and a few terminals for connections.   We could go a step further,
and make a board with the spring-loaded mini toggle and two LEDs soldered on it as well, so the whole thing just gets pushed through some holes in
the control panel, and is secured with the toggle nut, and the only wire connections to it are power and the two wires to the turnout itself.

[freescopesdad]

[peteski]

I looked at the data sheet of the relay Max mentioned and I'm not really sure how it works.  The info in there is not very clear to me, especially since there are 3 types of that latching relay being described with one or two coils. If I had one in-hand I could figure it out, but the datasheet alone is not doing it for me.

I do agree with Max is someone came out with a nicely etched PC board and installation instruction, that would make may Unitrak users very happy.
Max's design is good because it will reliably show the last selected route of the turnout (unless someone manually changes it). The only more reliable indicator would be to use a Hall effect sensor to monitor position of the switch machine's magnet. That would even show someone manually moving the switch lever.

[Point353]

Here's another option - the 751K - for controlling Kato turnouts that can also operate LEDs for position indication.

https://www.classixaudio.com/751D.HTM

https://www.classixaudio.com/pdf/751K.pdf

https://www.classixaudio.com/MRR_INDEX.htm